Unit 1: energy

• Biofuel


  A fuel that's made from recently living organisms
• Fossil fuels are also made from living organisms, but those organisms lived millions of years ago and were converted to fuel by a very different process
• Biofuels


  • Generally come from plants or algae
  • These organisms can photosynthesize and take up the sun's energy which can then be released later when we burn them for fuels
  • We can also use animal waste but this is often done at a much smaller scale
• Burning biofuels releases carbon dioxide


  Biofuels are normally thought of as being carbon neutral because they took up that carbon dioxide while they were growing
• Biofuels


  • They are effectively a renewable resource
  • They are relatively cheap to make
  • They are easy to transport and we can mix them with fossil fuels like petrol
• Using biofuels


  We can benefit from them without having to get new cars like we would if we wanted to use the electricity generated by solar or wind
• Growing biofuel plants


  It often means converting natural land, which could involve things like cutting down forests, releasing tons of CO2 even before the first crop of biofuels
• Harvesting, processing, and transporting biofuels

  It requires energy, which probably means more CO2 being released overall
• It is hard to tell how good biofuels really are, they are definitely not as good as we first thought
• When used properly, biofuels can be a great substitute for fossil fuels
• With all renewable energy resources, it's not all or nothing, we can choose to use biofuels where it does make sense and use something else where it doesn't
• Internal energy


  The total energy that's stored by the particles making up a substance or system
• Components of internal energy


  • Potential energy stores
  • Kinetic energy stores
• Potential energy stores (like gravitational and elastic potential) are not really related to temperature
• Kinetic energy


  The movement energy of the particles
• Heating up a substance

  Transfers energy to the kinetic energy store of all the particles, increasing their internal energy
• Temperature


  A measure of the average internal energy of a substance
• Some materials require more energy to increase their temperature than others
• Specific heat capacity


  The amount of energy needed to raise the temperature of one kilo of a substance by one degree Celsius
• Water requires 4,200 joules of energy to warm one kilo by one degree Celsius, whereas mercury requires only 139 joules
• Calculating change in internal energy

  Change in internal energy = mass x specific heat capacity x change in temperature
• In real life, the temperature increase would be less due to energy lost to the surroundings